1. Field of the Invention
The present invention relates to a method for manufacturing a spacer for an electron source apparatus, that spacer and an electron source apparatus using that spacer.
2. Related Background Art
As an electron emission device, two types of devices, i.e., a hot cathode device and a cold cathode device have been conventionally known. In regard to the cold cathode device, for example, a surface conduction emission device, a field emission device (which will be referred to as an FE hereinafter), a metal/insulation layer/metal emission device (which will be referred to as an MIM type hereinafter) are known.
As to the surface conduction emission device, for example, M. I. Elinson, Radio Eng. Electron Phys., 10, 1290, (1965) or another example which will be described later are known.
The surface conduction emission device utilizes a phenomenon such that an electric current is caused to flow through a thin film, which is formed on a substrate and has a small area, in parallel to the film surface to generate electron emission. As such a surface conduction emission device, there are reported a device using an Au thin film [G. Dittmer, “Thin Solid Films”, 9,317 (1972)], a device using an In2O3/SnO2 thin film [M. Hartwell and C. G. Fonstad, “IEEE Trans. ED Conf.”, 519 (1975)], a device using a carbon thin film [Hisashi Araki and et al., “Shinku (Vacuum)”, Vol. 26, No. 1, 22 (1983)] and others as well as the above-described device using the SnO2 thin film by Elinson and et al.
As a typical example of the device structure of these surface conduction emission device, FIG. 9 shows a top plan view of the above-mentioned device by M. Hartwell and et al. In this drawing, reference numeral 3001 denotes a substrate and 3004 designates a conductive thin film consisting of a metal oxide formed by the spattering method. The conductive thin film 3004 is made into an H-shaped planar form as shown in the drawing. When an electric process called an electric forming which will be described later is applied to this conductive thin film 3004, an electron emission section 3005 is formed. In the drawing, a distance L is set to 0.5 to 1 [mm] and a width W is set to 0.1 [mm]. Incidentally, although the electron emission section 3005 is illustrated in the rectangular form in the center of the conductive thin film 3004 for the sake of convenience, this is typical and the actual position or shape of the electron emission section are not faithfully shown.
In the above-described surface conduction emission device including the device by M Hartwell and others, it is general to form the electron emission section 3005 by performing the electric process called the electric forming with respect to the conductive thin film 3004 before carrying out electron emission. That is, the electric forming means that a constant direct-current voltage or a direct-current voltage which boosts at a very slow rate of, e.g., approximately 1 V/minute to the both ends of the conductive thin film 3004 to turn on electricity and the conductive thin film 3004 is locally fractured, deformed or transformed so that the electron emission section 3005 having an electrically high resistance is formed. It is to be noted that a crack is generated to a part of the locally fractured, deformed or transformed conductive thin film 3004. When an appropriate voltage is applied to the conductive thin film 3004 after the electric forming, electron emission occurs in the vicinity of the crack.
As an example of the FE, for example, W. P. Dyke & W. W. Dolan, “Field emission”, Advance in Electron Physics, 8, 89 (1956) or C. A. Spindt, “Physical properties of thin-film field emission cathodes with molybden um cones”, J. Appl. Phys., 47, 5248 (1976) and the other are known.
As a typical example of the FE device structure, FIG. 10 shows a cross-sectional view of the device by C. A. Spindt and et al. In the drawing, reference numeral 3010 denotes a substrate; 3011, an emitter wiring consisting of a conductive material; 3012, an emitter cone; 3013, an insulation layer; and 3014, a gate electrode. This device causes field emission from a tip of the emitter cone 3012 by applying an appropriate voltage between the emitter cone 3012 and the gate electrode 3014.
As another structure of the FE device, there is an example where the emitter and the gate electrode are arranged on the substrate in substantially parallel to the flat surface of the substrate, which is different from the lamination structure shown in FIG. 10.
Further, as an example of MIM, for example, C. A. Mead, “Operation of tunnel-emission Devices”, J. Appl. Phys., 32,646 (1961) and others are known.
FIG. 11 shows a typical example of the MIM device structure. FIG. 11 is a cross-sectional view, in which reference numeral 3020 denotes a substrate; 3021, a lower electrode consisting of a metal; 3022, a thin insulation layer having a thickness of approximately 100 Å; and 3023, an upper electrode consisting of a metal having a thickness of approximately 80 to 300 Å. In the MIM, the electron is emitted from the surface of the upper electrode 3023 by applying an appropriate voltage between the upper electrode 3023 and the lower electrode 3021.
Since the above-described cold cathode device can obtain electron emission at a lower temperature as compared with the hot cathode device, it requires no heater. Therefore, the cold cathode device has a structure simpler than that of the hod cathode device, and a finer device can be produced. A problem such as heat fusion of the substrate hardly occurs even if a plurality of devices are arranged on the substrate in the high density. Moreover, as different from the hot cathode device which has a low response speed because it operates by heat from the heater, the cold cathode device advantageously has a higher response speed.
Therefore, studies for applying the cold cathode device have been conducted at full blast. For example, since the surface conduction emission device has a very simple structure among the cold cathode devices and can be manufactured easily, a plurality of devices can be formed in a large area. Thus, as disclosed in Japanese Patent Application Laid-Open No. 64-31332 by the present applicant, a method for arranging plural devices to be driven has been studied.
Additionally, as to applications of the surface conduction emission device, for example, an image forming apparatus such as an image displaying apparatus or an image recording apparatus or a charged beam source and the like have been studied.
In particular, as an application to the image displaying apparatus, an image displaying apparatus using a combination of the surface conduction emission device and a fluorescent material which emits light by collision with electrons has been studied as disclosed in U.S. Pat. No. 5,066,883 by the present applicant or Japanese Patent Application Laid-Open Nos. 2-257551 and 4-28137. The image displaying apparatus using a combination of the surface conduction emission device and the fluorescent material is expected for the characteristic superior to that of the prior art image displaying apparatus adopting any other mode. For example, when comparing with a recently spread liquid crystal display apparatus, it can be said that the above-described image displaying apparatus is superior in that no back light is required because of the spontaneous light type or that a viewing angle is wider.
In addition, a method for arranging a plurality of FE devices to be driven is disclosed in U.S. Pat. No. 4,904,895 by the present applicant, for example. Further, as an example where the FE device is applied to the image displaying apparatus, for example, there is known a planar display apparatus reported by R. Mayer and et al. [R. Meyer: “Recent Development on Microtips Display at LETI”, Tech. Digest of 4th Int. Vacuum Microelectronics Conf., Nagahama, pp. 6-9 (1991)]
Furthermore, Japanese Patent Application Laid-Open No. 3-55738 by the present applicant discloses an example where a plurality of MIM devices are arranged to be applied to the image displaying apparatus.
Among the above-described image forming apparatuses using electron emission device, the planar display apparatus having a thin depth does not occupy a large space and has a light weight, and hence this apparatus attracts attention as a substitute for a cathode-ray tube display apparatus.
There is proposed a planar display panel section which accommodates in an airtight container an electron source substrate having the above-described electron emission devices arranged in the form of a matrix, and the inside of the airtight container is maintained at a degree of vacuum of approximately 10−6 [torr]. Therefore, as the display area of the display panel increases, means for preventing deformation or fracture of a rear plate and a face plate due to a difference in air pressure between the inside of the airtight container and the outside must be provided. As a countermeasure, a structure support (which is referred to as a spacer or a lib) which consists of a relatively thin glass plate and withstands the ambient pressure is provided between the electron source substrate and the face plate.